Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

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ORIGINAL ARTICLE Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

*1 2 1 Shrikant Baslingappa Swami , N.J. Thakor and P.R. Murudkar

Department of Agricultural Process Engineering, College of Agricultural Engineering and Technology, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Ratnagiri (MS)-415712, India.

Abstract In the present study the effect of three different yeast concentrations

i.e. 2.0, 2.4, and 2.8% and baking temperatures 230°, 240 °, and 250 °C on

baking time (min), hardness of slice (g), volume expansion (%), and whiteness index of bread was observed. These dependent variables were analysed for optimization of bread for nine treatments. All other ingredients *Corresponding Author: i.e. milk powder (2%), bread improver (0.03%), sugar (10%), salt (1.5%), vanaspati (3%) and oil (4%) water were kept constant. Sensory analysis of Shrikant B. Swami prepared bread by the various treatments was performed by coding different samples with market sample by using 9 point hedonic scale to get Email: [email protected] acceptable concentration of bread. Various sensory parameters of the bread were colour, texture, flavour, taste, mouth feel and acceptability was taken into consideration. Most accepted product from the sensory score was sample having yeast concentration 2.8% and baking temperature 240 °C. Received: 23/10/2015 The desirable quality of slice bread was based on the responses i.e. lower baking time, more volume expansion, more whiteness index, and lower Revised: 29/11/2015 hardness. The optimum zone for acceptability of bread was observed at baking time 20-21 min, volume expansion 665-718%, whiteness index 44- Accepted: 01/12/2015 46, and hardness of slice 10.0 - 10.5 g was observed at yeast concentration ° ° was 2.5 to 2.8% and baking temperature was 239.5 to 245.62 C. The quality parameters were correlated with sensory score for acceptability of the sliced bread. The bread can be prepared by using yeast concentration 2.5-2.8% and baking temperature 239.5 °-245.62 °C for lower baking time, more value of volume expansion, more whiteness index, and less hardness of slice.

: Bread, Yeast, Baking, Whiteness Index, Hardness, Volume Keywords expansion, Sensory analysis. 1. Introduction industry annually growing at a rate of 6 per cent. The Bread is a staple food product made from wheat organized sector is said to be growing a little higher whose worldwide mass manufacture is responsible for rate of 8 per cent. In 1977 Government had reserved significant energy usage and CO 2 emissions. Bread bread industry for small scale. However, Britannia production occurs on a number of different scales, from Industries Ltd (BIL) in private sector as which together the artisan bakeries serving the local community, to the accounted for 45 per cent of the total bread production large commercial bakeries serving entire nations, as in the country. In the unorganized sector it is said that well as in-store supermarket bakeries, small chain there are about 75000 bread manufactures spread all outlets and anything in between. There are many types over India including some of those operating from even of breads like white bread, brown bread, whole meal residential premises. South India consumes 32 per cent bread, wheat germ bread, wholegrain bread, granary of the total bread produced in the country followed by bread, rye bread, unleavened bread, sour dough bread, north consumes 27 per cent, west 23 per cent and east flat bread, hemp bread and crisp bread. Various consumes 18 per cent. ingredients used in bread preparation are maida, yeast, The composition of wheat is responsible for the sugar, salt, water, vegetable oil, milk powder, bread nutritional properties of bread. The properties of wheat improver, etc. are dependent on climate, soil and genetic variations The total bread production in the country is and therefore vary between wheat types. Wheat has estimated to be 3.75 million tons and the baking protein content that ranges from 8 to 13% and it also

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread has a high carbohydrate content of about 83% of the Zghal, 2008; Vanin et al., 2009). Optimization of the weight of the kernel. Other components of the wheat bread baking process is a subject of great importance grain include bran and germ. Bran is the outer coating for food industry. On the one hand, bread is a staple or “shell”, and is rich in B vitamins and minerals. The food and thus its production is relevant from a wheat germ or “embryo” is a rich source of B vitamins, commercial point of view, besides its cultural oil, vitamin E and fat. The wheat germ is removed relevance. On the other hand, baking is an energy- during milling as the fat tends to become rancid during intensive process due to water evaporation occurring in storage, although it is a valuable ingredients in its own the product (e.g. latent heat of water vaporization is right and is used in many products. Minerals contained 2.257 MJ/kg at 100 °C). The energy demand for a in wheat include calcium (151 mg), phosphorous, conventional baking process is around 3.7 MJ/kg, potassium (100 mg), iron (3.74 mg), magnesium (23 though it can be higher (up to 7 MJ/kg) depending on mg) and sodium (681 mg). Vitamins such as thiamine specific products and operating conditions (Purlis, (B1) (0.5 mg), riboflavin (B 2) (0.3 mg), folic acid and 2012). vitamins B 5 and B 6 are also distributed throughout the Each ingredient plays an important role in bread wheat grain. preparation. Mainly volume expansion related to yeast Yeast is the single- celled fungus. Baker’s yeast concentration, if it increases or decreases then directly is called as Saccharomyces cerevisia, “saccharo” volume of bread increases or decreases. During meaning sugar and “myces” meaning fungus. Yeast preparation of bread the yeast concentration and heat can metabolize simple sugar, such as glucose, sucrose, supplied should be in appropriate range. Considering and maltose. It is used to leaven bread and works by all the above points current study has been undertaken converting sugar into carbon dioxide, which causes the with an objective, to study the effect of yeast dough to rise so the bread will be light and airy. This concentration and baking temperature on quality of makes yeast an extremely important ingredients in the slice bread. production of the bread. Normally 2% yeast is added to the 100% of wheat flour (Mondal and Datta, 2008). If 2. Materials and Methods yeast concentration is increased then volume of dough Experiments were carried out in the Bakery also increases. So yeast is the main parameter in the Training Centre, Department of Agricultural Process bread preparation. Yeast is the driving force behind Engineering, College of Agricultural Engineering and fermentation, the magical process that allows a dense Technology, Dr. Balasaheb Konkan Krishi Vidyapeeth, mass of dough to become a well-risen loaf of bread. Dapoli. The quality analysis was carried out in NAIP The essentials of any bread dough are flour, water, and Laboratory of Department of Agricultural Process of course yeast. As soon as these ingredients are stirred Engineering. together, enzymes in the yeast and the flour cause large The study was performed on the three different starch molecules to break down into simple sugars. The levels of yeast concentrations (2.0, 2.4 and 2.8%) and yeast metabolizes these simple sugars and exudes a three different levels of baking temperature (230 °, 240 ° liquid that releases carbon dioxide and ethyl alcohol and 250 °C). The experiments were repeated three times into existing air bubbles in the dough. The dough has a for its replications. The results analyzed for strong and elastic gluten network; the carbon dioxide is optimization of bread quality parameters i.e. colour held within the bubble and will begin to inflate it. This (whiteness Index, hardness, baking time (min), volume phenomenon resembles blowing up bubble gum. As of expansion (%) and sensory evaluation (colour, more and tinier air cells fill with carbon dioxide, the texture, flavour, mouthfeel, taste and acceptability). dough rises. The total levels of treatment combinations were Baking is the final and most important step in 3×3×3= 27. bread production, and can be defined as the process which transforms dough, basically made of flour, water 2.1 Process for Preparation of Bread and leavening agents, in a food with unique sensory Fig 1 shows the process flow chart for features by application of heat inside an oven. In preparation of slice bread. The bread was prepared by particular, white or french bread is the most popular taking wheat flour (1 kg), sugar 100g, milk powder type of bread, and is distinguished for having a crunchy 20g, bread improver 3g, water 550 mL, along varied and golden-yellow (or brown) crust, a sponge and light yeast concentration i.e. 2.0, 2.4 and 2.8% into a crumb with soft texture and intermediate moisture, and planetary mixer. The ingredients are allowed to mix up a typical flavour. All these quality aspects are the result to 5 minutes for 39 rpm. The dough is allowed to keep of a series of physical and chemical changes produced as such for natural proofing in the same mixer at by simultaneous heat and mass transfer occurring normal temperature 20-22 ± 2 °C and relative humidity within the product during baking (Mondal and Datta, 80-95% for 25 minutes. The dough was added with salt 2008; Purlis, 2010; Sablani et al., 1998; Scanlon and

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd 132 Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

15 g and vanspati 30 g and allowed to mix up to 5 were kept in the oven. The breads should have minutes for proper mixing of salt and vanspati in the yellowish colour developed on its crust. When the crust same mixture at 39 RPM. The mixed dough was added get yellowish colour the time for baking was recorded. with edible oil 40 g and allowed to mix in the same The breads after achieving the yellowish colour was mixer for 20 minutes. taken from the oven and allowed to cool at room temperature 26 ± 2 °C for 2 h. Wheat flour (1 kg) + Sugar (100 g) + yeast (2.0, 2.4, The similar procedure was repeated for 2.4 and ° ° and 2.8%) + Milk powder (20 g) + Bread Improver (3 2.8% yeast concentration and at 240 C and 250 C g) + Water (550 mL) baking temperature. The similar observation i.e. volume expansion and baking time of the breads were recorded.

Mixing (5 min) in Planetary Mixer at 39 RPM 2.2 Estimation of Quality Parameters for Proofing (20-30 min) Breads

2.2.1 Moisture Content Moisture content of bread slice thickness 1 cm Addition of Salt (15 g) + Vanspati (30 g) was recorded by hot air oven method. 10 g sample was taken in moisture box. Weight of moisture box and sample was recorded. Moisture box without lid was Mixing (5 min) (39 RPM) placed in hot air oven at 105°C for 24 h. Then lid was placed over the box and sample was taken out and kept inside the desiccators for 10-15 min. Weight after Addition of Edible oil (40 g) & Mixing (39 RPM) (20 taking out sample from the dryer was recorded. min) Moisture content on wet basis was calculated by using Eq. (1). The experiment was repeated thrice for replication. The average moisture content was reported Moulding AOAC (2010).

Moisture % = × 100 ... (1) Proofing (RH 80%; Temperature 40 0C)

Where; w = weight of sample + moisture box; Baking (Temperature 230 °, 240 °, 250 °C) 1 w2 = weight of sample after drying + moisture box; w = weight of moisture box. Cooling (Room Temperature for 2 h)

2.2.2 Colour A colour of bread slice was measured under Slicing and Packaging Hunter Lab calorimeter. The Hunter Lab calorimeter was manufactured by Hunter associates Laboratory, Fig 1: Process Flow chart for preparation of bread USA. The equipment was standardized with standard black and white tile. The bread slices of 1 cm thickness The dough was now ready for shaping. 400 g of were kept on aperture of color measuring device. The above prepared dough was taken into the mould. The colour was measured as per 10°/D65 (ASTM) standard. mould was marked inside to get the change in volume It represents the colour in L, a and b value. Degree of in X, Y and Z direction. The volume of dough in the lightness or darkness of the samples was represented by mould was recorded and treated as initial volume. The “L” value, redness to greenness by “a” value and moulds were kept in the proofer and allowed to raise at yellowness to blueness by “b” value on hunter scale. 80% RH and 40 °C for 1 h. The moulds were taken out The experiment was repeated for 5 times and average from the proofer and volume expansion was recorded values were reported. The whiteness index was in X, Y and Z direction. The moulds were kept in the calculated as per the procedure described by Purlis deck oven for temperature 230 °C. The breads in the (2010) which is given in equation (2). moulds were observed continuously for each 2 minutes after 15 minutes interval from initial time when moulds = 100 − 100 − + + ... (2)

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd 133 Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

Where; Table 1 shows the effect of yeast concentration L = Lightness / darkness and baking temperature on moisture content of bread at a = Redness / greenness crust, crumb and bottom portion. Moisture content of b = Yellowness / blueness the bread at top (crust), crumb, bottom portion of the bread showed that the moisture content at top (crust) 2.2.3 Texture was 46.08 ± 1.10% db, crumb 66.63 ± 0.94% db, and The texture of slice bread was measured with bottom 42.76 ± 2.50% db. Effect of yeast concentration QTS texture analyzer. Texture analyzer was made by and baking temperature on bread has no much variation M/s. Brookfield Engineering Labs, Inc., USA. The in the final moisture content of the crust, crumb, and above mentioned slices were exposed to compression bottom portion of bread. force with Probe No. TA3/100 and pretest speed was 0.5 mm/s, compression depth was 4 mm, and trigger 3.2 Effect of Yeast Concentration and Baking load was 5 g for slice. For bread pretest speed 0.5 Temperature on Baking Time mm/s, compression depth 25 mm, and trigger load is 25 Fig 2(a) shows the effect of yeast concentration g the force deformation characterization were recorded and baking temperature on baking time of bread. It was from the instrument. The peak force for compression observed that as baking temperature increases from was reported. The experiment was repeated for 5 times 230 °-250 °C the baking time decreases 29 to 20 min. for its replication and average peak force (g) was Similarly as the percent yeast concentration of bread reported. increases the baking time decrease. It is also clear from contour plots Fig 2(b). The effect of yeast 2.2.4 Sensory Analysis concentration and baking temperature on baking time Sensory evaluations of bread prepared by using of bread is represented by equation (3) the combination of different independent variables were tasted by group of twenty-six peoples (sensory = 7.291 ɛ − 83.750 ɛ + 0.011 ɛ − 6.267 ɛ + panelists). They were from different age groups. Their 0.187 ɛɛ + 904.22 … (3) scores were co-related with the mechanical testing of the product. (R2= 0.998) For evaluation of bread the sensory parameters i.e. colour, texture, flavour, taste, mouth feel, and From equation (3) and contour plot it is clear acceptability. There are total ten breads were placed, that the combined effect of percent yeast concentration out of which nine were from the treatments and one and baking temperature will also reduce the Baking was control (Market sample- M/s Aiyangar Bakery). time. The samples were coded A-J. The sensory panel was Table 2 shows the ANOVA of baking time. It trained. The rating was based of nine point hedonic was observed that effect of yeast concentration (%) and scale. The standard format for sensory score sheet is baking temperature on baking time is highly significant given in Appendix II. The average scores were reported either at p ≤ 0.05 or p ≤ 0.01. for each treatment including the control sample (Market sample). 3.3 Effect of Yeast Concentration and Baking Temperature on Volume Expansion 2.3 Optimization Fig 3(a) shows the effect of yeast concentration The desired quality of bread slice should have and baking temperature on volume expansion (%) of more whiteness, less baking time, more volume of bread. It was observed that as percent yeast expansion, and less hardness. The desirable quality of concentration increases from 2.0 to 2.8% the volume bread were correlated with the response of whiteness, expansion increases from 520.0-770.7%. Similarly, as baking time, volume of expansion, and hardness with the baking temperature of bread increases the volume the sensory scores for different treatments of yeast expansion increases. It is also clear from contour plots concentration (2.0, 2.4 and 2.8%) and baking ° ° ° Fig 3(b). The effect of yeast concentration and baking temperature (230 , 240 and 250 C) using superimposed temperature on volume expansion of bread is given by contour plots. equation (4)

3. Results and Discussion = 12.812 ɛ − 1569.29 ɛ − 0.145 ɛ + 55.166 ɛ − 5.375 ɛɛ − 4923.07 ... (4) 3.1 Effect of Yeast Concentration and Baking Temperature on Moisture Content (R2= 0.997)

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd 134 Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

Fig 2(a): Surface plot of effect of Yeast concentration (%) and Baking Temperature ( oC) on Baking time (min) of slice bread. 250

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oC Temperature, Baking 236

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230 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Yeast Concentration, %

Fig 2(b): Contour plot of effect of Yeast concentration (%) and Baking temperature ( oC) on Baking time (min) of slice bread.

From equation (3) and contour plot it is clear Table 3 shows the ANOVA of volume that the combined effect of percent yeast concentration expansion. It was observed that effect of yeast and baking temperature will also increases the volume concentration (%) and baking temperature on volume expansion. expansion is highly significant either at p ≤ 0.05 or p ≤ 0.01.

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd 135 Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

Fig 3(a): Surface plot of effect of Yeast concentration (%) and Baking temperature ( oC) on Volume expansion (%) of slice bread.

250

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230 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Yeast Concentration, % Fig 3(b): Contour plot of effect of Yeast concentration (%) and Baking temperature ( oC) on Volume of expansion (%) of slice bread.

3.4 Effect of Yeast Concentration and Baking increase then decreases. Similarly, as the baking Temperature on Whiteness Index temperature of bread increases whiteness index first Fig 4(a) shows the effect of yeast concentration increases then decrease and again increase. It is also and baking temperature on whiteness index of bread. It clear from contour plots Fig 4(b). The effect of yeast was observed that as percent yeast concentration concentration and baking temperature on whiteness increases from 2.0 to 2.8% the whiteness index first index of bread is given by equation (5).

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd 136 Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

Table 1: Moisture Content at Crust (top), crumb (middle) and bottom of bread

Independent Variables Dependent Yeast Temperature Moisture Content (% db.) Concentration (°C) (%) Top Middle Bottom 2.0 230 42.67 66.59 42.68 2.4 230 42.79 66.62 42.79 2.8 230 42.84 66.66 42.85 2.0 240 42.65 66.59 42.65 2.4 240 42.74 66.63 42.73 2.8 240 42.81 66.65 42.82 2.0 250 42.70 66.67 42.71 2.4 250 42.78 66.64 42.78 2.8 250 42.85 66.66 42.85 Average 42.08 ± 1.10 66.63 ± 0.94 42.76 ± 2.50

Table 2: Analysis of Variance for Baking time

Degree of Sum of Mean F Significance Responses Freedom Squares Square P at 5% P at 1% F Regression 6 4718.810 786.468 Residual 3 6.194 2.064 8.94 27.9 380.899** Total 9 4725.00 - ** Significant at p ≤ 0.01; p ≤ 0.05

Table 3: Analysis of Variance for Volume expansion

Degree of Sum of Mean F Significance Responses Freedom Squares Square P at 5% P at 1% F Regression 6 3734090.0 622348.0 Residual 3 8767.910 2922.640 8.94 27.9 213.116** Total 9 3742860.0 - ** Significant at p ≤ 0.01; p ≤ 0.05

= 21.241 ɛ + 21.554 ɛ − 0.035 ɛ + Fig 5(a) shows the effect of yeast concentration 18.066 ɛ − 0.514 ɛɛ − 2250.030 … (5) and baking temperature on hardness (g) of slice of bread. It was observed that as baking temperature (R2= 0.998) increases from 230 °-250 °C the hardnessincreases. Similarly as the percent yeast concentration of bread From equation (5) it is clear that the effect of increases the hardness gradually decrease. It is also percent yeast concentration on whiteness index shows clear from contour plots Fig 5(b). The effect of yeast that, the whiteness index increases initially followed by concentration and baking temperature on slice of bread decreases gradually. As baking temperature increases is given by equation (6). the whiteness index decreases gradually followed by increase in whiteness index. = 44.416 ɛ + 169.775 ɛ + 0.066 ɛ − Table 4 shows the ANOVA of whiteness index. 28.270 ɛ − 1.636 ɛɛ + 3222.23 ... (6) It was observed that effect of yeast concentration (%) (R 2= 0.991) and baking temperature on whiteness index is highly From equation (6) it is clear that the combined significant either at p ≤ 0.05 or p ≤ 0.01. effect of percent yeast concentration and baking temperature will also decreases the hardness of slice of 3.5 Effect of Yeast Concentration and Baking bread.Table 5 shows the ANOVA of Hardness. It was Temperature on Hardness observed that effect of yeast concentration (%) and -

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd 137 Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

Fig 4(a): Surface plot of effect of Yeast concentration (%) and Baking temperature ( oC) on Whiteness Index of slice bread. 250

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230 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

Yeast Concentration, %

Fig 4 (b): Contour plot of effect of Yeast concentration (%) and Baking temperature ( oC) on Whiteness Index of slice bread. baking temperature on hardness is highly significant Desirable qualities of bread are lower baking either at p ≤ 0.05 or p ≤ 0.01. time, more volume expansion, more whiteness index, and lower hardness.Fig 5 shows the superimposed 3.6 Optimization of Dependents (Baking time, contour plots for effect of yeast concentration and Volume expansion, Whiteness index, and baking temperature on baking time, volume expansion, Hardness) whiteness index, and hardness of slice of bread.

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd 138 Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

Fig 5 (a): Surface plot of effect of Yeast concentration (%) and Baking temperature (oC) on Hardness (g) of slice bread 250

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230 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

Yeast Concentration, % Fig 5(b): Surface plot of effect of Yeast concentration (%) and Baking temperature ( oC) on Hardness (g) of slice bread.

It was observed that the lower value of baking of lower baking time, more volume expansion, more time 20-21 min, more value of volume expansion 665- whiteness index and lower hardness is shown in Fig 5. 718%, more whiteness index 44-46 and hardness of slice 10-10.5 g was observed in optimum zone where 3.7 Sensory Evaluation the yeast concentration was 2.5 to 2.8% and baking Table 6 shows the sensory scores for the slice temperature was 239.5 ° to 245.62 °C. The optimum zone bread. It was observed that eight breads having scored

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd 139 Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

Table 4: Analysis of Variance for Whiteness index

Degree of Sum of Mean F Significance Responses Freedom Squares Square F P at 5% P at 1% Regression 6 17744.2 2957.360

Residual 3 30.905 10.301 8.94 27.9 287.088** Total 9 17775.10 ** Significant at p ≤ 0.01; p ≤ 0.05

Table 5: Analysis of Variance for Hardness

Degree of Sum of Mean F Significance Responses Freedom Squares Square F P at 5% P at 1% Regression 6 3509.34 584.890

Residual 3 29.576 9.858 8.94 27.9 59.241** Total 9 3538.920 ** Significant at p ≤ 0.01; p ≤ 0.05

Table 6: Average Sensory scores for various samples (Sample A - J)

Sample Code A B C D E F G H I J Yeast Concentration (%) 2.0 2.4 2.8 2.0 2.4 2.8 2.0 2.4 2.8 1.0 Baking Temperature (ºC) 230 230 230 240 240 240 250 250 250 200 Sensory Attributes Colour 7 7 6 6 7 7 7 7 7 6 Texture 7 7 7 7 6 7 6 6 7 6 Flavour 7 7 7 6 7 7 6 7 7 6 Taste 7 7 7 6 6 8 7 7 6 6 Mouth feel 7 7 7 6 7 7 7 7 7 6 Acceptability 7 7 7 6 7 7 6 7 7 6 Overall Acceptability 7 7 7 6 7 7 6 7 7 6 Total Sensory Sore 49 49 48 43 47 50 45 48 48 42 morethan forty-five. Sample A and B are near aboutthe observed at yeast concentration 2.8% and baking acceptability limit but best score was observed at temperature 240 °C. This is lying within the optimum sample code F (yeast concentration 2.8% and baking zone of the superimposed contour plot. temperature 240 °C). Sample J was market sample Therefore it is recommended that the bread can which is not much accepted by judges. It had less be prepared by using yeast concentration 2.5-2.8% and concentration of yeast (10%). baking temperature 239.50 °-245.62 °C for the samples lower baking time 20-21 min, more value of volume 3.8 Correlation of Objective (Baking time, expansion 665-718%, more whiteness index 44-46, and Volume expansion, Whiteness index, and lower hardness of slice 10.0 - 10.5 g. Hardness) and Subjective (Sensory evaluation) Tests 4. Conclusions It was observed from Fig6 the optimum zone Following conclusions were drawn from the was observed in yeast concentration 2.5-2.8% and present investigation are as follows: baking temperature 239.50 °-245.62 °C. From the 1. Bread can be prepared by using yeast sensory scores it was observed that the best score was concentration 2.5-2.8%.

Journal of Food Research and Technology | October-December, 2015 | Vol 3 | Issue 4 | Pages 131-141 © 2015 Jakraya Publications (P) Ltd 140 Swami et al…Effect of Yeast Concentration and Baking Temperature on Quality of Slice Bread

2. Baking temperature should be 239.5-245.62 °C 3. Optimum baking time 20-21 min., volume expansion 665-718%, whiteness index 44-46 and hardness of slice 10.0 - 10.5 g.

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Fig 6: Superimposed contour plots showing the optimum zone

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